As an ordinary method for producing a trans-4-ethenylcyclohexane derivative, a method using a Wittig reaction of a cyclohexanecarbaldehyde derivative and methyltriphenylphosphine halide has been known (see, for example, Patent Document 1).

In this method, however, methyltriphenylphosphine halide as a raw material is expensive, and it is necessary to remove completely triphenylphosphine oxide by-produced for using the  resulting trans-4-ethenylcyclohexane derivative as a liquid crystal raw material, which requires a complicated purification process. Furthermore, a disposal cost is required for discarding the triphenylphosphine oxide by-produced, and thus the method involves problems in cost and environment.
As a method for producing the cyclohexanecarbaldehyde derivative used as a raw material of the reaction, a method of subjecting a cyclohexanone compound represented by the general formula (6) to a Wittig reaction has been known.

In the formula, R1 is hydrogen, alkyl having 1 to 15 carbons, alkoxy having 1 to 15 carbons, halogenated alkyl having 1 to 15 carbons, halogenated alkoxy having 1 to 15 carbons, alkenyl having 2 to 10 carbons, halogen or —C≡N; A1, A2 and A3 are each independently trans-1,4-cyclohexylene in which arbitrary —CH2— constituting the ring may be replaced by —O— or —S—, 1,4-phenylene in which arbitrary hydrogen may be replaced by fluorine, decahydronaphthalen-2,6-diyl, 1,2,3,4-tetrahydronaphthalen-2,6-diyl or naphthalen-2,6-diyl; Z1, Z2 and Z3 are each independently a single bond, —CH2CH2—, —(CH2)4—, —CH2O— or —OCH2—; and j, k and l are each independently 0 or 1.
As a method for producing the cyclohexanecarbaldehyde derivative, a method of oxidizing a carbinol compound  represented by the general formula (7) has been known.

In the formula, R1 is hydrogen, alkyl having 1 to 15 carbons, alkoxy having 1 to 15 carbons, halogenated alkyl having 1 to 15 carbons, halogenated alkoxy having 1 to 15 carbons, alkenyl having 2 to 10 carbons, halogen or —C≡N; A1, A2 and A3 are each independently trans-1,4-cyclohexylene in which arbitrary —CH2— constituting the ring may be replaced by —O— or —S—, 1,4-phenylene in which arbitrary hydrogen may be replaced by fluorine, decahydronaphthalen-2,6-diyl, 1,2,3,4-tetrahydronaphthalen-2,6-diyl or naphthalen-2,6-diyl; Z1, Z2 and Z3 are each independently a single bond, —CH2CH2—, —(CH2)4—, —CH2O— or —OCH2—; and j, k and l are each independently 0 or 1.
However, a cyclohexanecarbaldehyde derivative obtained by these methods is a mixture of a trans-isomer and a cis-isomer since the hydrogen atom at the α-position of the carbonyl group of the aldehyde is easily epimerized (isomerized). A trans-4-ethenylcyclohexane derivative that has a high trans-isomer purity is necessarily used as a raw material of a liquid crystal for attaining good electric and optical characteristics. Accordingly, it is necessary to remove the cis-isomer from the resulting cyclohexanecarbaldehyde derivative, but the cis-isomer cannot be easily removed, and purification with recrystallization and column chromatography is necessarily performed (see, for example, Patent Document 2). Thus, the  conventional methods are never satisfactory.
[Patent Document 1] JP H9-52851 A/1997 (U.S. Pat. No. 5,709,820)
[Patent Document 2] JP H9-124521 A/1997